1. Field of the Invention
The invention relates to reference circuits, and in particular to bandgap reference circuits capable of operating in low voltage environments while generating output with a nearly-zero temperature coefficient.
2. Description of the Related Art
Analog circuits incorporate voltage and current reference circuits extensively. Such reference circuits are DC quantities that exhibit little dependence on supply and process parameters and a well-defined dependence on the temperature. For example, bandgap reference circuits are probably the most popular high performance reference circuits, with the principle thereof to implement components having characteristics of positive temperature coefficient and negative temperature coefficient and add the voltages or current of these components in a predetermined proportion to generate a value independent of temperature, such value output as a reference. The conventional bandgap reference circuits use bipolar technology to create a stable low reference voltage at around 1.25V which is almost equal to the silicon energy gap measured in electron volts. However, in modem deep-submicron technology, a voltage of around 1V is preferred. As such, the conventional bandgap reference circuits are inadequate for current requirements.